Ok guys, I’m going to post this in several places, since I really need some help here. I’ve searched every archive I could find and I have seen similar questions posted, but no answers ever given.

I’m trying to adjust my timing on a forced induction c5. I’m getting some pretty bad knock around peak torque and I want to lower my timing in that range (the car is already running pig rich).

Here is where the problem comes in. I have adjusted each table in edit to only have 15 degrees of timing in the +.8 Gm/Cyl and the +3600rpm range (this is a big block of cells), but I’m still getting 18 to 19 degrees of timing when I’m under those conditions, according to EFILive.

I’ve literally made every table I can find demand that much timing in that range.
High Octane Spark Advance
Low Octane Spark Advance
Base Spark in Drive
Base Spark in Park
I also checked by IAT table, but those #s are 0 or negative.

The base Spark tables purpose have really thrown me off since the documentation that comes with ls1edit says it is used when the throttle is closed, which makes no sense since it has pretty big numbers for the airflow. Then again, it does seem to match up with what I see at idle, where the high and low tables don’t. I read somewhere else that the tables represent the minimal advance that will be observed. This is why I went ahead and lowered it to match up with my high and low tables.

I initially thought that EFILive may be lying to me, but in checking some of the other timing #s they seem to match up with the high advance table. The knock that I usually get actually drops me right down to about 15.

Can someone please explain what might be going on here. I’m really tired of experimenting. Is there a table that I’m missing? Does the timing decrease/increase at a engine revolution rate instead of what is demanded in the cell? Also, what happens between cells. Does it always use the previously entered cells values?

 

I just started tuning with LS1-Edit myself, but one of the local knowledgeable guys that's been helping me starts with +.6, not +.8. I wonder if that could be the issue?

- Dug

 

that's strange, cause i have the opposite , i have my timing set to 18 deg and i see 15 and lower.

how much boost are you pushing? my adjustments start from .76 and 4000 rpm.

check the spark retard limit table,IAT Vs. MAP table and make sure the nubers are either 0 or negative, and check the max KR vs. load and rpm to see that the numbers are either 0 or positive.
that's all i could think of right now.

hope this helps.

 

Thanks for the posts guys, but none of the suggestions seem to be the problem.

Here is the deal; I have plenty of logs that show my timing mapped out with gm/cyl and RMP.
Click Here for example

Notice how timing is around 18-19 when there is no KR and gm/cyl is +.8 and rpm is +4k. Well all of my tables in Edit say I should be at 15 advance in this range (and we are not talking about a small block of cells here). So I really think there is something non obvious going on here.

BTW, my IAT table is 0 or negative, so I’m sure that is not it.

I’ve posted on every board and list and emailed a few experts. I’ll be sure to post an answer if I ever get one.

 

please do post it if you find the problem, now not be a wise *** or something , but why not drop your timing some more ( say to 12 deg.) ????

 

Yes, I'm going to try that if I don't get any definitive answers (I’m out of town right now). I just got tired of the trial and error thing and I really stopped because I'm concerned about causing my engine to knock that much. I'm thinking about putting in some octane booster and then I can run more tests without any worries. Hopefully, someone will respond with the real answer.

 

Ok, I've done some more debugging and have started a new thread https://ls1tech.com/ubb/cgi-bin/ulti...&f=23&t=003561 , since it appears this issue is specific to '02 and up pcms.

I have found the pcm is adding 4 degrees of timing once I hit 3600 rpms. I subtracted an additional 4 degrees from all of those cells and the timing is now coming up very close to what I had originally entered. A post from a good source on another forum seems to indicate that this is common behavior on '02 c5s.